Production and Application

Production Processes for Cerium and Cerium Derivatives (Overview) 

Cerium is characterized chemically by having two stable valence states, Ce(IV) and Ce(III). This property is used in several production processes for the recovery of 

Whereas the fractional precipitation process will yield solid cerium-compounds the liquid-liquid extraction and ion exchange process will produce solutions of cerium. The cerium will be isolated usually by precipitation as an oxalate, carbonate or hydroxide. 

Cerium-oxalate, -carbonate and -hydroxide are considered to be the most important precursors for cerium-derivatives on a commercial scale. The cerium derivatives are yielded from these compounds by additional chemical and/or physical treatment. For example, cerium oxide may be formed easily by calcining cerium carbonate or/and cerium oxalate respectively. 

A fraction of Ce, La, Nd and Pr derived from bastnasite or monazite is a typical feedstock in the recovery process of cerium on a commercial scale. Separation of the rare-earth elements may be achieved by splitting the mixed rare-earth elements into a cerium/lanthanum and didymium (Nd/Pr) fraction first. The cerium/lanthanum fraction may be used as a further feedstock in a second extraction stage and will yield high pure cerium and lanthanum solution respectively. Cerium can then be precipitated as, for example, an oxalate or a carbonate which may be used as precursor for cerium derivatives. 

Most of the pigments used in conventional paints and coatings are also suitable for waterborne systems. Some exceptions are lead chromates and molybdates, manganese lakes (Pigment Red 48 and 52), some perylenes (Pigment Red 223), benzim-idazolone yellow (Pigment Yellow 151), and isoindolines (Pigment Yellow 13a) which all have limited alkali resistance. 

As a rule, pigments can easily be dispersed in water-soluble binders because the water-soluble binder molecules promote wetting and stabilization of the pigments. The dispersion and stabilization of pigments in polymer dispersions is, however, more difficult because the dispersions form a continuous phase in water and uniform distribution of the dispersed pigment particles in the paint film is hindered by coalescence of the polymer particles. To overcome such problems new dispersion additives have been developed in recent years. 

Corrosion-resistant and wear-resistant materials (e.g., stainless steel and in special cases suitable plastics) have to be used for the equipment required to produce and apply waterborne paints. This applies to production vessels, storage and transportation vessels, to the feed system used for application (e.g., closed circuit tanks, pipelines, and pumps) all of which must be able to withstand chemical mechanical stress. The use of corrosion-resistant materials for the spraying equipment is also advantageous. 

Waterborne paints should be protected against frost during storage. In general, storage areas do not have to satisfy special fire prevention regulations. 

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This heading covers such a large number of products and applications that it is difficult to give a complete inventory. For this reason the standards organizations, starting with ISO (International Organization for Standardization ), have published a series of standards to classify these products. 

Table 4. Manufacture, Production, and Application Data for Selected Aminonaphthalenesulfonic Acids...

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The basics observed in molded products are always the same only the extent of the features varies depending on the process variables, material properties, and cavity contour. That is the inherent hydrodynamic skin-core structure characteristic of all IM products. However, the ratio of skin thickness to core thickness will vary basically with process conditions and material characteristics, flow rate, and melt-mold temperature difference. These inherent features have given rise to an increase in novel commercial products and applications via coinjection, gas-assisted, low pressure, fusible-core, in-mold decorating, etc. 

As an alternative to electrochemical or radiolytic initiation, homolytic dediazoniation reaction products can be obtained photolytically. The organic chemistry of such photolyses of arenediazonium salts will be discussed with regard to mechanisms, products, and applications in Section 10.13. In the present section photochemical investigations are only considered from the standpoint that the photolytic generation of aryldiazenyl radicals became the most effective method for investigating the mechanisms of all types of homolytic dediazoniations —thermal and photolytic —in particular for elucidating the structure and the dissociation of the diazenyl radicals. 

Aehle, W. (2003) Enzymes in Industry Production and Applications, Wiley-VCH, Weinheim. 

Verbeken, D. Dierckx, S. Dewettinck. (2003). Exudate gums Occurrence, production, and applications. Applied Microbiology and Biotechnology, Vol.63, No. 1, (November 2003), pp. 10-21, ISSN 0175-7598. 

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